Activation of Optimally and Unfavorably Oriented Faults Within the Oklahoma LASSO Nodal Array
The LArge‐n Seismic Survey in Oklahoma (LASSO) dense nodal array with >1800 sensors captured multiple small (<1 km in length) seismogenic faults within its bounds. Using machine-learning based event detection methods (EQTransformer, Mousavi et al., 2020), we expanded the LASSO catalog by a factor of two to a total of roughly 2000 earthquakes located within the array. Using this extended catalog and FaultID (Skoumal et al., 2019) we algorithmically identify 38 separate seismogenic fault planes within the array’s footprint, a region covering 25 by 32 km. The focal mechanism catalog within the array is increased from 23 to 1306 events using machine learning methods and the model of Ross et al., 2018 to identify and characterize waveform first motions. The high-quality focal mechanisms within this catalog were then used to estimate the local principal compressive stress direction within the array’s bounds. The identified faults’ orientations are then compared to the inverted stress field to determine if the faults are optimally oriented. Optimally oriented faults require small stress changes to trigger failure, while unfavorably oriented faults require larger stress changes, assuming the same amount of accumulated stress on each fault. For induced earthquake sequences, the source of this stress change could be static stress changes from earthquake interactions and/or dynamic pore pressure changes. Within the context of the identified fault structures and their orientation to the local stress field, the spatiotemporal characteristics of each seismogenic fault’s behavior are used to understand if pore pressure or earthquake interactions played the dominant role in each sequence’s evolution.
Session: Imaging, Monitoring and Induced Seismicity: Applications to Energy and Storage
Type: Oral
Room: Grand C
Date: 4/20/2022
Presentation Time: 05:30 PM Pacific
Presenting Author: Colin N. Pennington
Student Presenter: No
Additional Authors
Colin Pennington Presenting Author Corresponding Author cpennington@usgs.gov U.S. Geological Survey |
Robert Skoumal rskoumal@usgs.gov U.S. Geological Survey |
Justin Rubinstein jrubinstein@usgs.gov U.S. Geological Survey |
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Activation of Optimally and Unfavorably Oriented Faults Within the Oklahoma LASSO Nodal Array
Category
Imaging, Monitoring and Induced Seismicity: Applications to Energy and Storage
Description